Mechanical linear actuators are used for translating rotational motion to linear motion. For example, ball screws are linear actuators that rely on a threaded shaft and a nut housing. The nut housing typically contains ball bearings that engage a helical raceway defined by the threaded shaft. Thus, rotational movement of the shaft translates into linear movement of the nut housing along the shaft. These types of linear actuators are often used in aeronautical applications, for example, to control movement of control surfaces, open and close windows, doors and/or access panels, and control the extension of landing gear. Linear actuators are also often used to convert rotary motion from an electric motor to axial movement of a steering rack in vehicular power steering systems and for precision control in robotic manufacturing.
Particularly in aeronautical applications, the failure of a mechanical linear drive system can have catastrophic consequences. The failure of one or more aspects of the drive system, such as the motor, the gear train, or the ball screw drive, may result, for example, in the landing gear of an airplane failing to extend or to extend into a fully locked open position. Accordingly, emergency systems are often provided that override and/or bypass the mechanical linear drive system to address such failures. However, these systems are often separate assemblies from the drive assembly, requiring additional space and hardware to accommodate the assembly. There is a need and desire for an actuator assembly that has an integrated emergency system, a system that automatically decouples aspects of the system from the normal drive configuration during an emergency.